Last summer Texas A&M research scientist and professor Dr. Jim Heilman released a report showing that Ashe Junipers, a.k.a. cedar trees, aren’t really the water hogs that people think they are. According to Heilman, “People have this idea that trees are suction pumps, that if you have all of this landscape and big trees, much more water is used. Not true.”

Historically the Edwards Plateau was a dynamic mosaic of grasslands and woodlands and much more savannah like. Cedars were found mainly in canyons where they were protected from wildfires. When settlers arrived, the introduction of cattle led to overgrazing, and, combined with the lack of fire, gave cedar the opportunity to expand its range and take over.

But does that mean that cedar is responsible for drying up our springs and consuming too much water? Not necessarily. Heilman’s research project is taking place at the Freeman Ranch just outside of San Marcos. Three key findings have come from his data:

First, in looking at water usage of brush compared to native grasses, the data show only “small increases” in the amount of water used. Common native grasses include little bluestem, switchgrass, big muhly, and hairy, tall, and sideoats gramas.

Second, many people consider cedars to be a “water thief,” based on the false belief that it has deep roots that tap into large amounts of water stored in limestone. In reality, Heilman discovered that live oaks surprisingly use more water than cedar trees. “Juniper roots are actually shallower than oak roots, and the internal plumbing of juniper greatly restricts the amount of water that can be taken up,” Heilman said.

Third, Heilman “found no evidence that deep roots were extracting significant amounts of water. Limestone bedrock in the Edwards Plateau is not capable of storing large amounts of water in the deeper zones for roots to tap into.” Essentially no matter which trees you have on your property, the thin layer of top soil present in most areas and the bulk of limestone prevent trees from soaking up large amounts of water. Ashe Juniper and Live Oaks are well adapted to our frequent drought conditions.

Implications for Brush Management
Just because cedars don’t soak up too much water doesn’t mean that you should keep them around. In areas where cedars are the dominant plant we call this a monoculture. Densely packed cedars prevent shrubs, native grasses and forbes from growing. These other plants are greatly beneficial for wildlife, much more so than Ashe Juniper. They provide seeds and fruit that are eaten by songbirds and small mammals. Flowering plants provide nectar for hummingbirds and bees. And of course they are a primary food source for white-tailed deer.

Coping with Drought – Rainwater Collection
The climate here in Central Texas has often been described as constant drought, interrupted every once in a while by a brief rain. While that might be a bit of a stretch, water is definitely a critical resource and isn’t getting any more abundant with a steady influx of people moving into the area. Over the next 50 years, water demand will increase by 30 – 40% or more. With many people already relying on ground water, periods of extreme drought will severely tax the aquifers.

Many people in the Hill Country are reducing their dependency on wells in favor of rainwater collection devices.

Advantages to rainwater collection devices are numerous. Best designs provide for gravity feed,
so you never have to worry about having power or having a pump go out. Rainwater is all natural with no additives or funny tastes. You won’t have to worry about a water softener or getting too much calcium in your plumbing. Rainwater collection devices are scaleable. You might want to start with a small tank, supplementing your well water. Most structures can collect enough rainwater to provide for personal use. Rainwater collection vessels range in size from several hundred gallons to 3,000 or more gallons.

Contact Plateau if you are interested in installing rainwater collection on your property.  We will work with you to determine your needs, complete a rainwater analysis, recommend the proper system, and get it installed.

Proper Brush Management
As shown in the picture, mass clearing of cedars can lead to significant problems because nothing is left but a thin layer of soil. The first good rain washes away the topsoil exposing rock. When Plateau is engaged to remove cedar, we come up with a plan that takes into account the landowner’s goals and takes advantage of technology to remove unwanted cedar without doing irreparable damage to the landscape. In most cases we prefer to remove secondary growth and trim or prune larger established trees. This allows us to maintain canopy cover at reasonable levels, while opening up the ground to promote native grasses and vegetation.

Senior biologist Keith Olenick tags cedars for complete removal or trimming.

by Brad Krimmel
Article from Plateau Land & Wildlife
Seasons Newsletter - Spring 2009

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